Remove most references to frog from lib/compiler .

lib/compiler/implementation/script.dart

Index: lib/compiler/implementation/script.dart
===================================================================
--- lib/compiler/implementation/script.dart	(revision 11103)
+++ lib/compiler/implementation/script.dart	(working copy)
@@ -3,10 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 class Script {
-  // TODO(kasperl): Once MockFile in frog/tests/leg/src/parser_helper.dart
-  // implements SourceFile, we should be able to type the [file] field as
-  // such.
-  final file;
+  final Mockfile file;
   final Uri uri;
   Script(this.uri, this.file);